Compensating balance-wheel



I. POVELSEN.

COMPEIMATING BALANCE WHEEL.

APPLICATION FILED MAR. 2, I920l Patented Aug. 17, 1920.

anotan,

INGILD POVELSEN', OF WASHINGTON, DISTRICT OF COLUMBIA.

COMPENSA'IING-l BALANCE-WHEEL.

Specification of Letters Patent.

Application filed March 2, 1920. Serial No. 362,877.

To all whom it may cof/wem .Be it known that I, INGTLD PovnLsnN, a citizen of the United States, residing at IVashington, in the District of Columbia, have invented a new and useful Compensating Balance-IV heel, of which the following is a specification.

My invention relates to balance wheels for watches, clocks and chronometers, and is especially useful in connection with marine chronometers and finely adjusted watches.

One of the objects of my invention is to provide a balance wheel which is non-magnetic and which will retain its shape and adjustment through repeated or extreme changes in temperature.

Another object of the invention is to provide a balance wheel which will have a minimum amount of air resistance in its oscillations and will be unaffected by barometric changes.

A further object is the provision of a compensating balance wheel having timing and temperature adjustments lying within, but operable from the outside of the wheel rim. This is for the purpose of permitting the adjustments to be effected without the usual distortion of the balance wheel which is experienced in the balance wheels heretofore used. Placing the adjustments within the rim serves to decrease air resistance.

One of the forms of balance wheels heretofore used has been constructed with a continuous rim connected with the wheel hub by spaced arms. Another consists of two curved arms projecting from the hub to form an approximate circle open at two points, each of the arms being formed of two metals of different coeicients of eX- pansion welded together. The rst of these forms is usually provided with metal protuberances on its periphery which act as compensating balance weights. These protuberances have the effect of increasing the air resistance to the oscillations of the balance wheel. Moreover, the method of adjusting the compensation means of such wheels is such as to make the wheel liable to become distorted through such adjustment.

In the second form of balance wheel above-mentioned, the two metals, although welded together, are put under great stress by their unequal expansion under the influence of temperature changes, the metals tending to separate and cause a distortion of the wheel.

Many of the balance wheels now in use are made of steel, and are consequently subject to magnetization, to the great detriment of the wheel and the accuracy of the entire instrument of which it forms a part. This is especially objectionable in marine chronometers, where the instrument is commonly surrounded by enormous bodies of iron` and steel, and in watches used in the vicinity of electrical machines.

To obviate these various objections and increase the accuracy of adjustment, thus insuring perfect compensation under all conditions and changes of temperature, I construct my balance wheel of a solid disk formed integrally with the rim and hub; so position the timing and compensating devices that they are entirely within the rim, leaving the outer surface of the rim smooth; and provide means for making all adjustments from without the rim, thus avoiding the distortion of the rim andthe destruction of the compensation relation.

My balance wheel is constructed, in its preferred form of non-magnetic metals, such as, for example, platinum, silver and gold, in order that it may retain its exact adjustment and perfect compensation in the presence of magnetic fields or influences.

To attain the above-mentioned objects I have devised the improved compensating balance wheel shown in the accompanying drawings, wherein Figure l is a plan view of the balance wheel with its cover removed, parts being shown in dotted lines for better illustration,

Fig. 2 is a` sectional view taken on line of Fig. l,

F ig. 3 is a side elevational view of the wheel mounted on the balance shaft, and

Fig. l is a sectional detail view taken on line y--y of Fig. 1. j

In its preferred embodiment my invention consists of a balance wheel having a solid continuous rim 1, rigidly attached by a solid disk 2 to the wheel hub 3 through which there is the usual opening 4 to receive the balanceshaft upon which the balance wheel is mounted. The disk, rim and hub are preferably made integral and of the same material throughout, preferably platinum. The integral con- Patcnted Aug. 17, 1920.

struction is employed to reduce the number of separate parts and minimize the opportunity for distortion. rlhe selection of platinum as the material best suited Ylor the construction of these parts is made because of its weight and small degree ot susceptibility to temperature changes. lt is to be understood, however, that the rim and hub may be ol separate pieces of metal rigidly lastened to the dislr, and that other suitable metals possessing a relatively high specii'lc gravity and a relatively low coeliicient of expansion may be used.

The balance wheel is provided with a cover 30 fitting closely upon the rim and oli the same diameter as the rim, so that the entire outer surlface of the 'ii/'heel is smooth and devoid ot protuberances liable to increase the air resistance to the oscillation of the wheel. The cover `iczfistened to the wheel by a nut 31, screwed on the upper screw-threaded portion of the hub, which projects through a central opening in the cover for this purpose.

rlhe adjustable parts of the wheel are positioned entirely within the rim and consist of timing` balance weights and comperr satin@` balance i'eights alternately placed around the inner periphery oil' the rim. The timing weights are adjusted to regulate the movement of the balancewheel irrespective oil the temperature conditions, while the adjustment of the compensating; weights is designed to afford the necessary regulation to oll'set any distortion due to temperature changes. The latter adjustment argely automatic and ordinarily reouires little or no manipulation, although means are provided for performing` manual adjustments to set the partsin the relation best suited to certain ranges of temperature and to render possible a linal minute aojustment where the precise degree olf exactness in compensation has not been attained by the device. .J

rlhe timing adjustment means comprises a hollow Vcasing 8, preferably of the same metal or alloy as the disk 2, the chamber 19 of the casing' being shaped to snugly receive a cylindrical weight 9 and permit its rotative and longitudinal movement therein. The weight 9 is preferably of gold, but may be oit any other metal or alloy having;`

approximately twice the coe'lllcient of eX- pansion as the metal of which the dish 2 is constructed. Fixed to the inner side of weight) is a screw 10 projecting through a screw-threaded opening' 11 in the inner wall 12 of the casing. The timing adjustment is effected by slightly changing` the position or" the weight 9 within the chamber 19, this adjustment serving' to move the weight inwardly or outwardly with respect to the circular line ol? gravity ot the balance wheel. The weight 9 may have a slot in its outer surface to receive a screw-driver or other instrument which may be inserted through an opening 13 provided in the rim 1 to enable the adjustment of this weight to be made. In the preferred forni oit my invention, however, l employ, as the means for turning the weight 9 and its guide screw 10, a dish le provided with a pair oit spaced prongs 15, 15, to project thro" similarly spaced slots 16, 16 through th `weight 9. Eislr 14 is held tightly on iti` seat 17 by a spring;` 18 and has a projc tinn head 181 litting snugly in the opening` 1,1; with its outer face flush with the surface o the rim, the head beingslotted rece-ive screw driver or other suitable adjustinfby instrument.

rEhe compensating adjiistment is effected through the opposite movement, during` temperature changes, olf the component parts of a plurality of compensating devices a-rranged radially about t1 hub 3 and il@ composed ot two or more metals or alloys havingdifferent coellicients of expansion. The specilic means employed consists of a plurality of weights, each composed ot a segmental portion 20 and an integral tabu`- lar portion 21 projecting lroml the inner side of the segmental portion toward the hub. The tubular portion Q1 has its end portion screw-threaded internally to receive the shank of a scre v lich has a head 25 by means of which it may be given a relatively small radial movement lfor linal vdji'istment of the wheel.

lllach compensating weight is sitioned on a rod 2%; .vhich pas the rim 1, weig' t portions' s and is rotatably seated in a whe side ot the hub 23. lied 'hreaded ior a portion oit its `age corresponding screvthi Y terior ot the screw 22 and is Lf 'l 1 n l I auch ilu-0. f

of the rim llush with the in the outer wall surface thereof.

Ccrews 27 are removably seA in tlc inn-rr face of the weight 20 and "lay be rcpiac d by heavier or lighter' screws whenever i is desired to vary the ymass olf' the weight 2U. rlhis feature furnishes an additional. adjustment ot' the wheel, its principal advantage beine to enable the proper adjustment oit the wheel for accurate compensation where the temperatureconditions are such as to render the ordinary compensating; means insulhcient to accomplish perfect compensation.

lt will be apparent that the compensation adjustment in reality comprisesA three adjustments, viz., the radial movement of weight elements 20, 01 and through turning of screw-rod 24:; the independent radial movement of weight-screw 92 in or out el the tubular weight-portion 21; and the placement ol the weight-screws 27.

To insure the satisfactory compensatory operation ol" the device, `he screw-rod 2i should L composed ot' a metal or alloy having a eoeiticient of expansion at least twice as great as the coellicient of expansion ot the metal or alloy of' which the other parts of the compensating device are composed. By way of illustration, in explaining the operen tien oft the invention, it vv .ll be assumed that the disk z id iis attached rim l are ot platinum and that the weight elements 20, 2l., 22 and ill? are of the saine metal, while the rod 2li is of silver, which has a coeiiicient of expansion approximately three times as great as platinum. lV hen the parts are properly adjusted for a certain temperature, a rise in temperature `vill then cause the disk and rim to expand, moving the rim 'farther away 'from the hub and tending to carry with it the weight elements resting on its surface. Simultaneously the v.f'eight elements, being of the same metal as the dislr and rim, will tend to move independently an eoinal distance away from the hub, by sliding along the disk toward the rim. The sum oi? these two expansions, which is tvv'icc. the unit of expansion o'f platinum, represents the extent of outward travel oil the weight elements if unimpeded. But while this is tahing place, the silver rod 3 is expanding three times as much as taie platinum j iarts, and, being prevented from moving longitudinally in the direction of the rim by the washes.' 2S which is fixed to the rod 2i and abuts the inner side olf the ri i., the lo?, ifadinal expansion is naturally in the opposite direction, that is to say, inwardly. v'iuliicient clearance is provided tween the end oi the rod and the inner wall ol the socket Q5 to permit such long'tudinal travel o i rod lr. rlChe inward expansion of rod 2s'- carries with it the connected pai 9 and 2f), the weight elements 2l and E20 heing nxed to the rod through the screwthr aded (onneetion lietween screw 2Q' and la' th Y tnhular weight portion 2l aml the rod 2l. Thus, under compulsion. oit the expanding silver rod, the tendency oi the weight elements to move outwardly two units is overcome and these parts are actually moved inwardly one unit. rlhis amount oi inward movement exactly compensates the outward movement of the rim one unit and the original balance is maintained. H the expansion of the silver rod falls short oi being sufficient to counteract the outward expansion oi? the rim, a further adjustment may be made hy turning screw 22 to\.vard the huh, thus lengthening the active part ot the compensating weight and increasing the amount oi1 its longitudinal expansion!Y In this way any slight discrepancy in the resu ng action ot the unequal expansion oli the two difiere-nt metals may he oliviated or corrected. This can also be done hy chang ing screws 2T, as heretofore described.

lt will also he apparent that the weight of the timing device, beiner ot gold, which has twice the coellicient or' expansion oi' platinum, will not he carried outward by the outward expansion oi the platinum rim and disk, but will retain its same relative Yposition with respect to the other `liarts.

l claim:

l. A balance wheel comprisingl a hub, a rim, and a solid disk connecting said rim to said hub.

2. il balance lwheel comprising a hub, a rim, a solid disk connectingr the rim to the hub, and a cover attached to t ie wheel.

3. A balance wheel comprising a hub, a rim, a` solid diskconnecting the rim to the huh, and a cover on the wheel resting upon the free edge of the rim.

4. A balance wheel comprising a hub, a rim, a member connecting the rim to the huh, and a cover on the wheel.

A balance wheel comprising a hub, a rim, a memher connecting the hub and rim, a cover on the wheel, and timing and compensating devices positioned Within the rim and adjustable from without the rim.

6. In a balance wheel, a huh, a rim, a member connecting the hub and rim, compensating devices positioned within the rim, means for performing ordinary adjustments sai-d devices from without the rim, and

ional means within the wheel for further adjusting said devices.

ln a balance wheel, a. huh, a rim, a memher connecting the rim to the hub, compensating devices positioned within the circumference oil the rim and adjustable from without the rim, and timing devices also positioned within the circumference of the rim and adjustable from without the rim.

8. In a balance wheel, a hub, a rim, a member rigidly connecting the rim to the l1 ub, and a compensating device positioned within the rim, said compensating device comprising a radially disposed rod of relatively high coetlicient ot expansion fixed at one end and free to move longitudinally at the other end, and a weight having a relatively low coe'licient of expansion slidably resting on the member which connects the hub and rim and fixed at one end to said radially-disposed rod.

9. In a balance wheel, a hub, a rim, a member connecting said rim to said hub, timing devices positioned Within the rim, and compensating devices positioned within the rim, said timing devices and compensating devices being arranged in alternating relation around the wheel.

10. In a balance wheel, a compensating device comgrising an outwardly expansive element ot a low coeflicient of expansion element of a low coe'iicient'o expansionV slidably positioned on said wheel within the rim thereof and'V free to expandv longitudinally in an outward direction, said weight element being connected to asecond expansive member of a relatively high coeiiicient of expansion which is free to expand only in an inward direction.

18. In a balance wheel, a compensating device comprising a plurality of compensating members having different coecients of expansion and so constructed and arranged as to be expansible in opposite directions.

1li. In a balance wheel, a compensating device comprising a plurality oi? compensating members within the rim of the wheel and adjustable from without the rim, said compensating members being so constructed and arranged that each is capable of expansion in a direction different from the expansive direction of any other of said members.

15. In a balance wheel, a compensating device comprising an outwardly expansive compensating weight of a relatively low coeihcient of expansion, an inwardly expansive member of a relatively high coeiiicient of expansion, said outwardly expansive member being slidably mounted on said inwardly expansive member and having one end iixedly connected thereto, and means for adjusting the length of the active part of the said compensating weight.

16. In a balance wheel, a'hub, a rim, a member connecting the hub and rim, a radially disposed rod fixed at one end vto the rim and so engaging the hub at its other end as to permit of inward radial expansion, a compensating weight member slidably supported upon the member which connects the rim and hub, 'said compensating weight member being mounted upon the radial rod with its inner end secured thereto, whereby the radial rod is adapted to expand only in aninward radialdirection and the compensating weight member is adapted to expand only in an outward radial direction.

17. In a balance wheel, a hub, al rim, a member connecting the rim and hub, a compensating device positioned within the rim, said compensating device comprising a radially disposed rod oitl relatively high coeiiicient of expansion iixed at one end and free to expand radially at the other end, a compensating weight of relatively low coeilicient of expansion slidably resting upon the member which connects the rim and hub and ixed at one end to the radially disposed rod, means for adjusting the length of the compensating weight, and means :tor varying the weight of said weight.

18. In a balance wheel, a hub, a rim, a member connecting the rim and hub, a compensating device positioned within the rim, said compensating device comprising a radially disposed rod of relatively high coeiiicient oi expansion ixed at one end and free to expand radially at the other end, a compensating weight of relatively low coeilicient of expansion having a segmental portion and a rod portion, means on the segmental portion' for varying the weight oi the compensating weight, and means on the rod portion for varying the length of the active part of the compensating weight, the compensating weight being fixed at one end to the radially disposed rod and free to expand radially at its other end.

19. In a balance wheel, a .compensating device comprising a member expansible relative to said wheel only in an inward radial direction, and a second member expansible only in an outward radial direction.

INGILD POVELSEN. 

